Two months ago he was at the electric keyboard to help his favorite punk group, Polyrock, record its first album for RCA in New York. That done, composer Philip Glass flew to Rotterdam to supervise the premiere of Satyagraha, his three-hour opera on the early life of Mahatma Gandhi, sung in Sanskrit, it is being lavishly staged by the Netherlands Opera Company. Glass has been one of the most popular of the serious contemporary composers since his surrealistic, four-and-a-half-hour opera Einstein on the Beach became the hit of European avant-garde circles in 1976. Subsequently, it was a sellout at New York's Metropolitan Opera. Traditionalists no longer consider the 43-year-old Glass a musical lightweight. In fact, it was the staid Rotterdam city council that commissioned Satyagraha (for $30,000) to open its opera season. Enthusiastic applause indicated the gamble paid off.

Satyagraha (which means "truth's force") is set between 1893 and 1914, when Gandhi was living in South Africa. An attorney, he found himself the target of discrimination as a dark-skinned Indian. In a series of tableaux, the three-act opera tells of Gandhi's experiments with nonviolence as a weapon against officially sanctioned racial prejudice. Commenting on the action is a chorus of 40 voices intoning Sanskrit texts culled from the Bhagavad-Gita. The combination is powerful; the opera's staging and spiritual force struck a New York Times critic, who like almost everybody in the audience could not understand a single word, as "reminiscent in mood of Wagner's Parsifal."

Like all recent works by Glass, the opera's music is as harmonically bold as Home Sweet Home and as repetitive as a TV jingle. After the curtain fell opening night, the composer could not hide his pleasure at hearing his melodies, often as simple as a scale, being hummed in the foyer of the theater. Their appeal is broad—from the serious music lover tired of feigning interest in atonalities to the rock crowd (David Byrne and David Bowie are fans) which finds surprising appeal in Glass' highly structured music. Declares Bowie, "It's the most commercial sound around, a fact that only Philip and I know." An occasional feature of a Glass concert is the incidence of pot smoking in the audience. It happened at the Met during Einstein on the Beach (but not among the burghers of Rotterdam at Satyagraha). The composer shrugs at the phenomenon. "I don't think smoking dope has anything to do with my music," he says.

Then why do listeners refer to his compositions as "head music"? "With my work," Glass explains, "one of the first things people perceive is expanded time, or loss of time, or no time whatever. It's a nonordinary state, but not in any way the same as a drugged state. Being stoned is a state of inattention, and I think my music takes complete attentiveness. We exist in an age of psychological frontierism with all these Daniel Boones. Some of them are into dope. Some are into meditation. Some into electronics. And some are into my music."

Glass, the son of a Baltimore record shop owner, started playing the flute as a boy. He earned a degree in mathematics and philosophy at the University of Chicago before settling into Juilliard in New York. He earned to compose in the Schoenberg-Berg-Webern atonal and 12-tonal styles, with a few American touches out of Charles Ives and William Schuman. A Fulbright grant sent him to Paris in 1966, where he studied with the austere Nadia Boulanger. "There are still people who think I've had no musical education," Glass exclaims. "They think I'm some kind of primitive."

While in Paris he collaborated with the Indian sitar player and raga composer Ravi Shankar on a film score. Turning away from Boulanger's conservative ways, he began composing the not-quite-so-simple-as-it-seems music that has made him famous. Divorced from his wife, off-Broadway theatrical director Joan Akilaitis (they alternate custody of their children, Juliette, 11, and Zachary, 9), Glass works in a four-room apartment on Manhattan's Lower East Side. This month he is scheduled to marry Dr. Luba Burtyk, a 28-year-old internist.

In Satyagraha, Glass is confident he has an enduring hit. "We've had 70 years of pieces since Schoenberg that no one understands," he argues, "so there's nothing really wrong, is there, with a little contemporary music being appealing?"